Device for distributing wood chips in pulp digesters



Dec. 27, 1 932. B. F. SMITH DEVICE FOR DISTRIBUTING WOOD CHIPS IN PULPDIGESTERS Filed Dec. 5. 1931 Patented Dec. 27, 1932 UNITED STATES PATENTOFFICE BERNARD F. SMITH, OF AIPLETON, WISCONSIN, ASSIGNOR T0 PAPERPATENTS COI- IANY, OF NEENAH, WISCONSIN, A CORPORATION OF WISCONSINDEVICE FOR DISTRIBUTING WOOD CIIPS PULP DIGESTERS Application ledDecember This invent-ion relates to the general art of paper making, andhas reference more particularly to an improved mechanism fordistributing wood chips in pulp digesters.

The general object of the invention is to provide an apparatus wherebythe chips may be so distributed in the digester as to effect, in thefirst place, more uniform cooking conditions through a more uniformtemperature dist-ribution within the digester, thereby improving theyield and quality of the pulp;

and, in the second place, to secure a larger charge of chips beingintroduced into the digester than is possible by the procedureheretofore practiced by reason of a closer piling of the chips, thusconsiderably increasing the capacity of the cooking equipment.

In the present customary method of filling digesters with chips, a spoutis placed over the top nozzle of the, digester, and the sliding gate inthe chip bin bottom immediately above the spout is opened. The chipsfall bv gravity through the spout and into the digester. As is the casewith all materials in small pieces, a cone-shaped pile is formed in thedig-ester. the entering chips dropping on the apex and sliding down to aposition of rest somewhere along the sides of the pile. The chips.having a slab-like form or shape, tend to take a position of most stableequilibrium. which means that they will rest on one of the faces havingthe greatest surface area, rather than on one of the edges. They slidedown the cone in this position, with the result that a charge of chipsis formed in the digester having a stratification corresponding to theangle of repose of th'e material. Not infrequently a stream of chipsdropping from the bin enters the top of the digester eccentrically, andthis leads to a stratification apex line somewhat eccentric to thevertical center line of the digester. However. the angularity of thestratification still exists.

Considering now the effect of this peculiar stratification upon thecooking process, after the digester is filled with chips and cookingliquor is introduced, the vessel is usually iilled to the top with there-agcnt and sealed by a top nozzle cover or cap, whereupon the heatingot the contents is begun. Two methods of 5, 1931. Serial No.l 579,226.

at regular intervals in one horizontal plane of the surface of thebottom cone. The steam is quickly condensed to water by the cookingliquor and gives up its latent heat, as well as a portion of itssensible heat, to the latter. This warm liquor rises by convectionthrough the digester contents, displacing colder liquor above, whichfalls t0 the bottom of the digester, is heated and, in turn, rises. Thusa convection current of circulation develops in the liquor portion ofthe digester contents. As the contents warm up the vapor pressure of theliquid, and also gas pressure of the dissolved sulphur dioxide in caseof sulphite cooking liquor, causes a development of pressure in thedigester. Further, the condensed steam increases the liquid content ofthe digester, causing it to lill up and develop a hydrostatie pressure,which is usually allowed to reach a predetermined maximum and is thenmaintained at this point by relief of excess water vapor, sulphurdioxide gas ahd liquor through suitable outlets in the top nozzle. Therelief of sulphur dioxide gas, in the sulphite process particularly,aids also in maintaining a circulation of the liquid content. The gas isreleased in the form of bubbles, and these rise through the digester,causiplg upward motion of the liquid surrounding t em.

Now, the liquid must naturally flow in channels formed by theinterstices between the chips. And if the chips have an angularstratiiication, such. as results from the usual method of filling, thechannels or interstices must be somewhat continuous in the direction ofthe angular alignment or stratification. Since these channels leadupward and away from the walls of the digester to its axis, the liquidstream in rising tends toward the axis or center of the digester, and indescending it follows the outside walls of the vessel because of thecooling eiiect resulting from radiation of heat from these walls. Hence,the

tion, itfh'asan 'adverse effect n'ponfthe pulp.

quality and yield. It leads to non-uniformityin the product, inasmuch aspart of the wood is :eipofs'ed 'thCQCQOking-reagent at a highertemperatreforatmuch longer time than other parts l. Naturally, thecooking process is not cmplteduntil all the wood has been convertedinto,.pulp,1and by the time the contents of the colder zones arecompletelyconverted, the contents' of the warmer central zones .will beconsiderablyv overcooked, resulting-in" 'a Hveryi' appreciable yield andv strength losszwhich,1`coursfe,is undesirable. lAmore modern systemofhfvcooking involves' the'forced'circulation' of hot -cooking liquorthrough ltherdige'ster,v accomplished by withdrawingthe liquor from thetop or bottom of the ldi'gester, passing yit through a pump, and

vforcing itfback intoj-th e-dige'ster at the bottom or top", as fthecase maybe. This modificationis less -Vproductivejof zones of unequaltemperatures in thejfdigester,"bu`t its eiiiciency in thisffres'p'ectlis not complte. The angular stratification-of the chips causes most ofthe liquor, tio' `flow vrthrough the central zone ofthefdig's't'erifithe'liquorisforced in at the bottom gbi: along thewalls ifideli'vered at the l. Atopi and this leadsfto somewhat inactivezones in' thediges'ter' contents which are not pulped as rapidly asvbody: 'of the contents. The'Qpresentfinvention aims to eliminatetheundesirable c :ditionsliiithe digester outabove, and'fnploys, asthemain feature "of .the invention, ya novel device in the nature of"aufv eccentric cone; rotatably. suspended in the' digester'slightlybelow the charging nozzle of the latterandr'ldisposediin the path of Flthe [falling stream of cfhfipsn,I for creating a substantiallyhorizontal1strati`fication of the chips 'inthe fdigester'andacloserpacking of the same,l bywhic'hV ai morel uniform cooking andacnsiderableincrease thepulp ob- ,tained feach' charger are secured.

.The-A invention, its 'mdeof operation, and

the benefits, and y advantages inherent therein will `lall ,beYunderstoodfand appreciated'byf:personsfvfamiliar with this branch of,the'fpap'er making/art fromv the following detailed description, `takenin, connection with the accompanying drawing', wherein I haveillustratedpnepractical and simple form in which` .invention maybeembodied, and VHWShCh-l-il i `I Vig..flfiska.. view in i verticalaxallsectionofa pulp digester and its chip-distributing mechanism,illustrating the substz uitiallyl lhorizontal stratification of thecharge obtained by the use of the present distributor.

Fig. 2 is a vertical section on an enlarged scale through the upperportion of the digester and its nozzle, showing the improved device fordistributing the inflowing stream and effecting the horizontalstratification of thechargey 1.1..' i

Fig. 3 is a further enlarged axial section of the anti-friction bearingmember for the shaft of thecone(distributor. -v

Fig. 4 is a top plan View of the ,cone distributor, in section throughits shaft on the line 4-4 of'Fig. 2.

Figr 5 is an enlarged side elevation of the cone distributor and itsshaft, partly broken out and in section, showing a countersunlr bushingthrough which the cone is keyed to its shaft.

Referring to the 4drawing-10 designates a vdigester of the usual formhaving a conical bottom portion 11 and a charging nozzlev 12;

and at 13 is indicated in Fig. 1 a pipe for steam or hot cooking liquorentering the lower end of the di gester.

14 designates a sleeve of-a size to have an easy sliding fit in thecharging nozzle 12 and formed on its upper end with an annular flange 15resting on the upper end of the nozzle. To the lower end of the innerwall of the sleeve 14 are attached, as by soldering, welding, orotherwise, equally spaced pairs of angle-attaching strips 16, betweenthe in- I wardly projecting limbs of which are riveted or otherwisesecured the outer ends of a plurality of downwardly and inwardlyinclined flat spider arms17 secured at their inner ends to a verticalbearing casing 18. In the upper and lower ends of the casing 18 areanti-friction bearings 19 and 20 of the ball type that are locked inplace by upper and lower lock nuts 21 and 22. These lock i nuts engagethreaded portions 23 and 24 of a vshaft section 25, which latter isformed with upper and lower annular shoulders 26 and 27 against whichthe inner rings of the bearings 19 and 20 are pressed by thelock nuts 21and 22. These spaced anti-friction bearings afford a rigid and nearlyfrictionless lateral support for the rapidly rotating shaft 25; theY.construction,permitting the filling ofthe space Within the bearingcasing 18 with a suitable lubricant (not shown) and the escape of thelubricant Abeing guard-y ed against by upper and lower glands 28 and 29attached to the ends ofthe casing 18 by` screws 30. and internallygrooved to receive packing rings 31.

32 designates the main operating elementA I of the chip distributor,this, in the embodiment of the inventionherein shown, taking the form ofan eccentric truncated cone. This cone member may be made of wood, metalor any other materialwell adapted to withstand the wear of contact withthe falling stream of chips impinging thereon and dellected thereby. Asshown in Figs. 2 and 5, the lower portion of the shaft 25 extends somedistance below the bearing 18, and the cone 32 is formed with aneccentric axial bore 33 that is fitted ont-o the lower end portion ofthe shaft 25 from below the latter. The cone 32 may, of course, be fixedon the shaft to rotate with the latter by any suitable or desired means,but in Fig. 5 I have illustrated an attaching means well adapted tomaintain the cone in rigid relation to the shaft under the considerableunbalance of the cone caused by its eccentric mounting when in veryrapid rotation. The lower end of the axial bore 33 is formed with astepped countersink comprising a wide shallow portion 34 and a narrowerdeeper portion35. Fitted within this countersink 1s a bushing comprisinga body portion 36 filling the deeper countersink 35, and a head or Bangeportion 37 filling the shallow colintersink 34. The bushing is locked onthe shaft by an ordinary key 38 engaging registering keyways in theshaft and bushing and the bushing is locked to the cone by screws 39passed through the ange 37 and into the body of the cone. The lower endofthe shaft 25 is preferably tapered, as shown, and the bore of thebushing is correspondingly tapered to insure a tight fit and prevent anylooseness or wobbling of the cone on the shaft due to wear. The lowerend of the shaft is threaded to receive a nut 40, by which, and theusual cotter piny 41, the cone and its bushing are securely locked onthe shaft.

The cone and its shaft may be driven by any suitable drive extendingthrough the charging nozzle. but I have herein illustrated the use of afiexible drive shaft 42 extending axially through the sleeve 14 andsuitably coupled to the upper end of the shaft 21 as by means of aknurled nut 43 secured to the lower end of the fiexible `drive shaft 42.I may here state that after the digester has been filled with chips andbefore the contents are subjected to the digesting operation, it is, ofcourse, necessary to remove from the charging nozzle 12 the chipdistributor and its supporting means. By providing a ilexible driveshaft 42, the entire assembly can manifestly be withdrawn from thecharging nozzle by simply lifting out supporting sleeve 14. In actualpractice, the flexible `shaft 42 is suspended from an overhead trolleycarrying a motor and a drive from the motor to the shaft 42; but asthese features form no part of the present invention, I have not deemedit necessary to illustrate the same herein.

When loading the digester, the chips are directed into the upper end ofthe charging nozzle 12 through a suitable guide chute or hopper; and thedescending stream of chips hereinabove set forth, are

imiun, which is sufliciently inclined to direct the chips outwardly tothe circumference of the digester; so that, so far as the downwardsliding of the chips is concerned, the chi s are deiected at widelyvarying angle's to e `axis of the digester, In addition to this slidingaction of the chi s, the cbne also tends, by its rapid rotation, tothrow the chips olf tangentially. The combined result of this slidingaction at varying angles and tangential iinpellin action is to scatterthe chips with substantial uniformity throughout the entire crosssection of the digester, so that the body of chips builds up in the digester with the substantially horizontal stratification indicated in thebeneficial results of the invention, as

secured.

I claim:

1. The combination with a pulp digester, of mechanism for distributingchips therein, comprising a conical member formed with a downwardly andoutwardly tapered chi -de fleeting surface presenting varying ang es ofinclination to its axis, means for rotatably mounting said conicalmember below the charging nozzle of the digester in the path of 'thestream of chips, and means for rotating said conical member.

2. The combination with a pulp di ester, of mechanism for distributingchips t erein to create a substantially horizontal stratification of thechips in said digester, comprising a conical member of roundcross-section formed with a chip-defiecting surface resentingprogressively increasing angles o clination to its axis from a minimumto a maximum, means for rotatably mounting said conical member below thecharging nozzle of the digester with its axis the airis of said nozzle,and means for rotating said conical member.

3. The combination with a pulp digester, of mechanism for distributingchips therein, comprising a truncated eccentric cone, means forrotatably mounting said cone below the chargin nozzle of the digester inthe path of the fa ling stream of chips, and means rotating said cone.

4. The combination with a pul digester, of removable mechanism fordistrihuting chips therein, comprising a sleeve slidingly fitting withinthe charging nozzle of the digester and formed lwith a flange on its upr end resting on said nozzle, a vertical aring member supported by saidsleeve, a vertical shaft journaled in and extending below said bearingmembei',`a truncated eccentric in line with Fig. 1, whereby mounted onthe lower end of said shaft, and a drive shaft coupled to the upper endof said first-named shaft.

5. The combination with a pulp digester, of removable mechanism fordistributing chips therein, comprising a sleeve slidingly fitting withinthe charging nozzle of the digester and formed with a flange on itsupper end resting on said nozzle, a. vertical bearing member having armsattached to said sleeve, a vertical shaft journaled n and extendingbelow said bearing member, a truncated eccentric cone formed with anaxial bore mounted on the lower end of said shaft, said bore having acountersink at its lower end, a flanged bushing lling said countersinkand keyed to said shaft, means for attaching the flange of said bushingto said coneJ and a drive shaft coupled to the upper end of saidfirst-named shaft.

BERXARD F. SMITH.

